As water-purifying equipment for filtrate plants that purifies natural water into clean water, water-purifying equipment in which coagulation settling tanks and sand filtration equipment are combined have been conventionally used in a large number of applications. There are issues with such equipment that the equipment tends to be large in scale, a construction cost thereof is high, automation thereof is difficult, operation and management thereof are not easy, many chemicals such as aggregating agents are added thereto, it is difficult to improve water quality, and so on. Recently, various membrane filtration water-purifying systems using high-performance filtration films have been proposed and implemented as alternative equipment.
In such a membrane filtration water-purifying system, the performance and lifetime of a filtration film serving as a filtration medium are factors of key importance. From this point of view, the development of a high-quality filtration film and the development of a simple monitoring system that detects damage to a filtration medium and monitors its performance degradation have been in demand.
As a filtration film, a film called a hollow-fiber membrane module has been conventionally developed and used. This is a film in which several thousands to several tens of thousands of hollow fibers are bundled and housed in a case housing to form a module. As a system for monitoring performance degradation by damage thereto; a system in which an optical sensor is equipped so as to sense bubbles generated by making air invading from the outside to the inside of a hollow-fiber membrane; a system in which a gaseous body including fine particles is made to flow into a hollow-fiber membrane module, and a number of fine particles in the gaseous body passing through the hollow-fiber membrane is measured by a fine particle meter equipped with a laser light source; a system in which a secondary side of a hollow-fiber membrane is made into a full-capacity state with water, a given gaseous body is pressure-fed from a primary side, and a quantity of water pushed out from the primary side to the secondary side of the hollow-fiber membrane is measured after the pressure of the gaseous body is kept a certain pressure for a given time, and so on have been proposed to apply to various methods and apparatuses (for example, Patent Documents 1 to 4).
A water quality meter attached to a part of a distributing water pipe of water works distributing water system is also disclosed wherein the meter comprises an analyzer that analyzes sample water guided from the distributing water pipe and a guiding part composed of a single member having a plurality of supply channels for supplying a plurality of liquids including the sample water in the analyzer (for example, Patent Document 5). Further, a particle diameter distribution measuring apparatus comprising a sample liquid circulating system and a sample liquid measuring system is disclosed wherein the apparatus is improved by adding a step of applying ultrasonic to the conventional drain method such that a frequency of cleaning cycles and an amount of waste fluid are decreased (for example, Patent Documents 6 and 7).
Moreover, a method comprising the steps of detecting weight of insoluble fine particles utilizing that the laser beam is scattered by the insoluble fine particles and judging the completion of dissolution is disclosed (for example, Patent Document 8).
Further, a detection method comprising the steps of collecting optical beams from a coherent light source, focusing the beams on something in a flow of liquid including fine particles, detecting a change of diffracted light generated in the optical beams, and measuring the number of fine particles is disclosed (for example, Patent Document 9). Further, a measurement method for measuring fine particles in liquid comprising the steps of irradiating a laser beam inside a fluid liquid, detecting scattered light from fine particles floating in the liquid, and measuring characteristics of the particles such as particle diameters and the number of particles is disclosed (for example, Patent Document 10).
However, those are implemented as the operation of the membrane filtration water-purifying system is temporarily stopped such that it is not possible always to monitor the water. Further, in case that impurities in the flow channel of the filtrate water pipe line system is too few, or that impurities are unevenly dispersed in the flow channel, it may not be possible to shoot and analyze images therein. Further, those are not designed for detecting damage to the filtration film, and configurations thereof are different. Then, it is difficult to identify ruptured pieces of the film since images including various sizes of mixed impurities are detected when the film is broken.
[Patent Document 1] JP-A-2000-342937
[Patent Document 2] JP-A-2004-216311
[Patent Document 3] JP-A-2005-013992
[Patent Document 4] JP-A-H10-024283
[Patent Document 5] JP-B-3551073
[Patent Document 6] JP-A-2000-155088
[Patent Document 7] JP-U-A-H06-35948 (Utility Model)
[Patent Document 8] JP-A-2002-82025
[Patent Document 9] JP-B-3151036
[Patent Document 10] JP-B-H07-86457